Idle ok on startup,then won't go below 2k after it gets up to temp.

this is what i found about code f85




QUESTION: 1991 Sedan Deville, 4.9 port injection
Car runs great until outside temp reaches 92 deg. or above. the car will start to cut out under load (take off or hill. if i pull over the car will idle fine rev the engine to a steady high rpm and it will cut out. i had a code e44 (o2 sensor rich)so i replaced o2 sensor with no effect. the other code received was f85 (Throttle body service required). I have checked all connectors and hoses attached to the throttle body. all ok. looking inside throttle body there ar two tubes under the flaps one is totaly restricted with a black buildup and the other partly blocked. Not sure what these tubes do and if that could cause engine to cut out when hot and under load. any ideas?

ANSWER: You found your problem which is this black residue which when hot turns to a jelly substance and blocks the idle air passage. You need to clean all that residue from the throttle body and do not forget to spray the small hole in the side of the throttle body just behind the throttle plate.

At hi mileage,you may want to clean the throttle body(if there is carbon buildup,the computer can't compensate for it because the idle position required to avoid stalling won't be consistent).I was also wondering if this is a "drive by wire"setup-no throttle cable.If so,you may have an issue with the stepper motor in the throttle body.(this design hadn't come out yet when I quit working on cars for a living in 97,so this is just a guess)

Hello my name is autoteck21 sounds like you dealing with one of two things. #1 Either you have a vacuum leak in one of your hoses or your vacuum box at the worst case one of your vacuum control solenoid. #2 Your idle air control module (under your throttle body.)
To test #1 take a can of brake clean or carb/choke cleaner and in small 2-3in areas spray little spots while engine is running listen too your idle for any changes (you will here the differences) if so there's your leak.
To test #2 find the little connector (2 wire) under your throttle body (when standing in front of your car lower front side under intake pipe hose clamp)

A high idle is caused from a vacuum leak, check the vacuum hoses for cracks, worn against something, any elbows need checked, IAC (idle air control) you will hear a hissing sound, remove the intake tube just before the throttle body and listen for the IAC to close it won't draw as much air if it's working correctly, try cleaning the IAC with throttle body cleaner.

Idle problems are almost always a filthy throttle body, which is the most common thing to go wrong with our I6 engines. Clean this first, but disconnect the battery before you do it. We don't have a traditional PCV valve, so the throttle body gets dirty easier than other cars. Must be cleaned at least once a year or more depending on your driving habits.

Spark plugs other than AC Delco 41-103, or the Iridium versions of NGK, Or Denso won't idle as good also. Take Autolight, or Bosch for example, won't idle very well, or last as long.

These two things are the most common, if these don't fix it, check for vacuum leaks, new air filter, upstream 02 sensor. From there, it's gets more in depth and should look to a professional.

all the codes point to throttle body. clean throttle body, especially around throttle plate. check for loose wires, if problems persist. replace throttle body. p2104 is tac system forced idle, p2111 is tac system stuck open, p2112 is tac system stuck closed. clean throttle body good, and see if this fixes it. then go from there. have a good day !!

It means that the throttle body is dirty and the deposits in the throttle bores are restricting air flow at idle to the point that the idle speed control has no more authority to maintain the correct idle speed.

Take the air cleaner off, hold the throttle wide open and look down the throttle bores. Spray the throttle bores with carb cleaner and scrub the bores and backside of the throttle blades with an old toothbrush. Cleaning the deposits off the bores and throttle blade backsides it will restore the idle air flow to the correct level. When the throttle body is clean, disconnect the battery negative cable for 60 seconds to reset the idle learn offsets to the "clean throttle body" default values.

While you are in the throttle body and looking down the bores....see the two tubes sticking up at you from the intake manifold floor just below the throttle blades...??? Those are the EGR tubes and they are NOT supposed to be full of carbon and crud. Rod them out thoroughly with a piece of stiff wire to remove the deposits. Go all the way down thru the tubes to the cast passage below and make sure that they are clean and unrestricted so that the proper amount of EGR can flow.

Turning the key to the run position extends the ISC anticipating a restart, so if the setting is incorrect it would not erase a hard code. Just turning the key to run would light up both the service soon and service now lights as a bulb check, in other words, letting you know the bulbs work. Do you have the factory service manual?

The ISC adjustment is simple on this car. With the engine running and at operating temperature, You raise the throttle arm slightly with your right hand and push the shaft of the ISC in to fully retract it with your left hand. With constant pressure on the ISC shaft it will slowly retract. The very second it bottoms, you quickly remove the wiring connector to the ISC. Now you should have a very low idle and a gap between the throttle arm and the tip of the ISC. Approx. 0.060 of an inch. Once you know the gap is correct, shut off the engine, wait 10 seconds and reconnect the ISC wiring. Restart the engine and the ISC is set to spec. The TPS setting must be verified at this time. At minimum idle, ISC not touching the throttle arm, and unplugged, the TPS should be reading approx .0 or .1. Once the ISC is reconnected, you should see a TPS reading of approx. .5 at idle. with the A/C off.

A hard code can be erased but will continue to reset as long as the reason for it has not been corrected. Idle learn procedures were designed into later year engines with multi port fuel injection to adjust idle regardless of the amount of coke build up within the throttle body. Your fuel injection system does not build up coke or deposits because the 2 injectors spray down thru the throttle body, effectively cleaning the throttle body while running. Alot of owners adjust the ISC as if it were a throttle stop screw on a carb. guessing as they go. The ISC and TPS "MUST" be in sync to get the best off throttle response and smoothest idle. Adjusting the ISC without verifying gap or TPS voltage usually results in a surging or too high warm idle. You say the car failed at idle. For what reason? CO or HC? or idle too high?

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you will need to do a base idle adjustment bridge the diagnostic pin out and the earth pin out black wire and white and black trace(i think) on the diagnostic connector the engine fan should run at any temp and the check engine light should flash this takes out the ecu operation of the vehicle therefore it will be like a carbie(make sure the vehicle is at or close to operating temp) disconnect the IAC connector then adjust the throttle stop screw to get the right base idle 6-800 rpm while slowly blocking off the iac hole inside the throttle body(may stall a couple of times but persist) with this in mind this is also the way to get flash codes from the ecu just with ignition on terms still bridged first flashes are 10s short break then units eg. two flash=20 three flash after= code 23 long break next code and so on 12 is system ok

it smoths out because you can't here the miss check fuel pressure and check for vachum leaks and build up on throttle plate.

Could be a defective or dirty Idle Air Control Valve.It is a part of the engines throttle body assembly.Get a can of throtle body cleaner and follow the instructions on the can. This is a common problem a many cars.